1. Field of the Invention
The present invention relates to a recording system, and more particularly, it relates to an ink jet recording system having a recording means for performing the recording by discharging ink toward a recording medium.
2. Related Background Art
In recording systems such as printers, copying machines, facsimiles and the like, or recording systems used as output terminals of composite electronic equipments or work stations including a computer, word processor or the like, an image is recorded on a recording medium (recording sheet) such as a paper sheet or a plastic film on the basis of image information. Such recording systems can be grouped into ink jet recording systems, wire dot recording systems, thermal recording systems and laser beam recording systems in accordance with the recording type.
In a serial recording system of serial scan type wherein a main scan is effected in a direction perpendicular to a recording medium feeding direction (auxiliary scanning direction), after the recording medium was set at a predetermined recording position, an image is recorded (main-scanned) by a recording means mounted on a carriage movable along the recording medium to perform a one-line recording, the recording medium is then line-spaced by a predetermined amount (pitch feeding), and then a next image is recorded (main-scanned) on the stopped recording medium to perform a next one-line recording. By repeating such recording operations, the recording is effected on the whole recording medium (one-page recording). On the other hand, in a recording system of line type wherein the recording is effected only by the auxiliary scans in the recording medium feeding direction, after the recording medium was not at a predetermined recording position, a one-line recording is performed en bloc, the recording medium is then line-spaced by a predetermined amount (pitch feeding), and then a next one-line recording is performed en bloc. By repeating such recording operations, the recording is effected on the whole recording medium.
Among the above-mentioned recording systems, the recording system of the ink jet type (ink jet recording system) performs the recording by discharging ink from a recording means (recording head) onto the recording medium, and has advantages that the recording means can easily be made compact, that a fine image can be recorded at a high speed, that an image can be recorded on a plain sheet without any treatment, that the running cost is cheap, that there is substantially no noise due to non-impact recording type, and that a color image can easily be recorded by using plural color inks. Moreover, in the ink jet recording system of line type utilizing the recording means of line type having a plurality of discharge openings arranged along a width of the recording medium, the recording can be effected at a higher speed.
Particularly, in the recording means (recording head) of the type wherein the ink is discharged by using thermal energy, a recording head having liquid passage arrangement (discharge opening arrangement) with high density can easily be manufactured by forming electrical/thermal converters, electrodes and liquid passage walls patterned on a substrate and a top plate through etching, depositing and sputtering techniques, thereby making the head more compact. On the other hand, there are many requirements for the materials of the recording medium. Recently, thin paper sheets or worked paper sheets (such as filing punch-perforated paper sheets, paper sheets with perforated lines, or paper sheets having various configurations) have been requested, as well as plain paper sheets or resin films (OHP sheets).
In the above-mentioned ink jet recording system, there has been generally adopted an operation that a predetermined amount of ink is discharged at a predetermined position in the system immediately before a normal recording operation (for recording an image on a predetermined position of the recording medium by discharging a predetermined amount of ink) is effected after a power source of the system is turned ON or after the system has been left in an operative condition for a predetermined long time with the power source being turned ON.. Such an operation for discharging the ink in other than the normal recording operation is referred to as "preliminary discharge".
The purpose of the preliminary discharge is as follows. In the ink jet recording system, since the image is formed on the recording medium by selectively discharging the liquid ink from the discharge openings of the recording head, particularly under the low temperature and low humidity circumstances, the ink tends to be hard to discharge from the discharge openings because of an increase in the viscosity of the ink due to the vaporization of ink liquid or the low temperature at the discharge openings. Thus, if the normal recording operation is immediately started after the recording system has been left for a long time, at the initial phase of the recording operation, it is feared that the poor recording such as the imperfect image formation or ink deflection occurs. To avoid this, immediately before the normal recording operation is performed, an operation is performed so that the viscosity of the ink near the discharge openings is returned to the normal condition by discharging a predetermined amount of ink from the discharge openings of the recording head to discharge the viscous ink near the discharge openings, i.e., the preliminary discharge operation. By effecting such preliminary discharge, it is possible to prevent the occurrence of the above-mentioned poor recording.
However, in conventional ink jet recording systems, in many cases, a position was set out in a widthwise direction of the system, where the ink ejected by the preliminary discharge could be received (i.e., a position where the preliminary discharge is effected) outside the width of a maximum recordable recording medium (recording sheet and the like). Thus, a space exclusive to the preliminary discharge had to be reserved, with the result that the width of the recording system had to be increased accordingly, thereby making the recording system less compact.
By the way, in the past, as shown in FIG. 21, many small-sized recording systems such as word processors, printers, portable calculators are of a so-called serial type wherein the recording is effected by reciprocally shifting a carriage 151 mounting a recording head 150 thereon in a widthwise direction of a recording sheet 152. In such a serial recording system, the carriage 151 on which the recording head 150 is mounted is reciprocally shifted along a guide shaft 153 arranged in parallel with the recording sheet 152. The guide shaft 153 is normally inserted into through holes 154c formed in side plates 154a, 154b of the recording system and is fixed with respect to a longitudinal (thrust) direction thereof by fitting E-rings into grooves formed in both ends of the guide shaft or by securing one end of the guide shaft to at least one of the side plates by means of a holder plate 155 as shown in FIG. 21.
However, in the above-mentioned arrangement for regulating the longitudinal movement of the guide shaft 153, since the E-rings or the holder plate 155 must be used as mentioned above, the number of parts is increased and the assembling processes are also increased, thus comprising the operability and making the system expensive.